JEE Advanced Chemistry Question (2026) — Solution

Step-by-step solution

Statement (A) is incorrect: Nitric acid ( HNO _3) is a strong oxidizing agent that oxidizes both glucose and gluconic acid to saccharic acid. Statement (B) is correct: Fehling's reagent provides an alkaline medium. Under these conditions, fructose (a ketose) undergoes the Lobry de Bruyn-van Ekenstein rearrangement to form an equilibrium mixture of fructose, glucose, and mannose. Glucose and mannose are aldohexoses that readily reduce Fehling's solution, giving a positive test. Statement (C) is correct: Hydrolysis of sucrose (a disaccharide) yields an equimolar mixture of D-(+)-glucose and D-(-)-fructose. This mixture is known as invert sugar because the sign of specific rotation changes from positive (for sucrose) to negative (for the mixture). Statement (D) is incorrect: The specific rotation of L-(-)-glucose is -52.5^ , so for D-(+)-glucose it is +52.5^ . The specific rotation of L-(+)-fructose is +92.5^ , so for D-(-)-fructose it is -92.5^ . The specific rotation of invert sugar (an equimolar mixture of D-glucose and D-fructose, which have the same molar mass) is the average of their specific rotations: [ ]_ mix = +52.5^ + (-92.5^ ) 2 = -20^ . Answer: Fructose gives a positive Fehling's test because it isomerises to glucose and another aldohexose in the presence of Fehling's reagent.; Invert sugar is an equimolar mixture of D-glucose and D-fructose formed after hydrolysis of the corresponding disaccharide.